CallManager existing call muted when a second one was answered

[Enrico Pasqualotto]

Hello, I've a strange issue on a old CUCM (9.1.x) and my infrastructure a composed as follow:

ISDN lines -> VGW (2800) -> CUCM -> SIP trunk to 2° PBX-> Phones

Issue seems isolated on phones registered to a second PBX linked with a SIP trunk on CUCM.

Not always but 50% of times, when a call is established from outside (ISDN) to phone connected on second PBX and a new one arrive when answered the first one goes in mute (both side) and sometimes the external caller hear beep like hold or record tone.

Phones connected directy to CUCM doesn't have this issue (seems).

From a packet capture on the second PBX we saw that audio from CUCM IP simply stop goes in mute, audio to CUCM is present on capture but never arrive to external caller.

In the same capture between CUCM and SIP PBX I can't see any SIP event like update or similar.

Any suggestion on where start looking for troubleshooting?

Thanks

[Elliot Dierksen]

Silence with a periodic beep is normal behavior if there is no MoH server available in the MRGL of the device where the call entered the network (meaning the gateway). Does audio resume if the internal IP phone picks the call back up?

The MoH audio file # is determined by the called/destination device. The MoH server is determined by the calling/originating device.

[Enrico Pasqualotto]

No the beep isn't with a constant frequency seems random.

Call answered by phone1 (and muted when phone2 anwer the second call) isn't resumeable. The only action possibile is hangup as caller and called see the call online but no audio.